Fuel burners in ducts



April 5, 1960 R. R. JAMISON ETAL 2,931,175

FUEL BURNERS IN DUCTS Filed Jan. 27, 1958 3 Sheets-Sheet 1 In ventors yMWVHOTH s April 1960 R. R. JAMISON ETAL 2,931,175

FUEL BURNERS IN DUCTS 3 Sheets-Sheet 2 Filed Jan. 27. 19,58

Inventors 14 a :2 $911 By @4 Home 5 April 5, 1960 R. JAMISON ETAL2,931,175

FUEL BURNERS IN DUCTS Filed Jan. 27. 1958 S Sheets-Sheet 3 37 III- 1 l nventorr v Home 5 United States Patent FUEL BURNERS 1N DUCTS Robin RalphJamison and Ian Bruce Ogilvie, liristol, England, assignors to BristolAero-Engines Limited, Bristol, England, a British company ApplicationJanuary 27, 1958, Serial No. 711,213

Claims priority, application Great Britain January 29, 1957 11 Claims.(Cl. 6039.82)

This invention relates to equipment for burning fluid fuel in afast-moving'stream of gaseous combustion-supporting medium confinedwithin a duct. Such equipment may for example form part of a ramjetengine or an after-burner for a turbo-jet engine.

It is well known that the principal elements of equipment of this kindare: means for dispersing the fuel into the fast-moving stream, meansfor igniting the fuel, and a flame holder. The latter commonly takes theform of an assemblage of radially extending and/ or ringshaped guttershaving their open sides facing downstream. The equipment also frequentlyincludes means enclosing a pilot combustion zone wherein the flows ofcombustionsupporting medium and fuel are maintained at values mostfavourable for the maintenance of stable combustion.

The object of the present invention is to provide an assembly of suchelements which will combine operating efiiciency with economy ofmanufacturing cost and convenience of handling.

According to the invention, equipment for the purpose set forthcomprises an island member in the duct having a hollow rear end portionconstituting a pilot combustion zone open at its downstream end, aplurality of hollow vanes open at each end extending lengthwise along arear part of the island member and outwardly across the passage betweenthe island member and the duct, each vane comprising two internalpartitions dividing the hollow interior into a middle chamber and frontand rear end chambers, openings in the wall of the island memberconnecting the front and rear end chambers with the pilot combustionzone, means in each middle chamber for supporting an igniter of a kindcapable of projecting a flame, openings in the wall of the island memberthrough which flame from the igniters may enter the pilot combustionzone, openings in the duct, normally closed by closure members, throughwhich the igniters may be inserted and withdrawn, and means fordispersing fuel into the pilot combustion zone and into the passagebetween each adjacent pair of hollow three-chamber vanes. The means fordispersing fuel into the passage may itself be between the vanes or liea little upstream from them.

In this assembly the rear end chambers of the hollow vanes constituteflame holding gutters opening into and radiating from the pilotcombustion zone. Preferably these gutters are supplemented by one ormore ringshaped flame-holding gutters arranged intermediately betweenthe duct and the pilot combustion zone, the ringshaped gutters openinginto the radiating gutters.

According to a feature of the invention the depth of the rear chambers,that is their dimension lengthwise of the duct, is two or more times thedepth of the ringshaped gutters.

According to another nature of the invention the rear vane partitions,constituting the bottoms of the radiating gutters, slope generallyoutwardly and rearwardly so that the depth of the gutters at theirjunction with the part of the island member constituting the pilotcombustion zone is greater than the depth of the gutters near the duct.

According to another feature of the invention the forward vanepartitions, constituting the outer walls of passages conveyingcombustion-supporting medium into the pilot combustion zone, slopegenerally inwardly and rearwardly so as to deflect thecombustion-supporting medium entering through the open forward end ofthe vanes progressively towards the openings in the island memberconnecting the passages with the pilot combustion zone.

According to another feature of the invention the island member isformed with a manifold chamber surrounding a central rearwardlyextending projection provided with a fuel conduit and carrying a fueljet arranged to disperse fuel in the downstream direction into the pilotcombustion zone, the'manifold chamber being separated from the pilotcombustion zone by a ring of swirl-producing blades radiating from theprojection, and being connected to the front end chambers of the hollowthree-chamber vanes by the openings in the wall of the island member towhich reference has already been made.

According to another feature of the invention the part of the islandmember carrying the rearwardly extending projection is provided with atleast as many radiating projections each provided with a fuel conduit asthere are hollow threechamber vanes, these radiating projectionsextending into the passage between the island member and the ductbetween each adjacent pair of hollow threechamber vanes and carryingfuel jets for dispersing fuel into the passage.

Preferably one such radiating projection is provided extending into thepassage between the island member and the duct between each adjacentpair of hollow threechamber vanes, each projection carrying a fuel jetarranged to project fuel in an upstream direction and a fuel jetarranged to project fuel in a downstream direction.

In a preferred embodiment having the features of the last precedingparagraph each radiating projection forms part of a fin knife-edged ateach end and extending be tween the island member and the duct, the partof each fin constituted by the radiating projection carrying on eachside a lateral projection provided with a fuel conduit, each lateralprojection carrying, in axial alignment with one another, a fuel jetarranged to project fuel in an upstream direction and a fuel jetarranged to project fuel in a downstream direction.

According to another feature of the invention the parts of the vanesconstituting the front end chambers of the vanes are made as a unitarycasting with the part of the island member constituting the manifoldchamber and the central and radiating projections. The remaining parts,that is to say the part of the island member constituting the wall ofthe pilot combustion zone and the parts of the vanes constituting themiddle chambers (igniter housings) and the rear end chambers (radiatinggutters), together with the ring-shaped gutter or gutters if used, aremade of heat-resisting sheet material.

Where the equipment according to the invention is used as part of aramjet engine the temperature of those parts referred to as being madeas a unitary casting remains sufficiently low for suc hcasting to bemade of a light weight metal alloy.

Further features of the invention will be apparent from the followingdescription of a constructional example applied to a ramjet engine inwhich reference is made to the accompanying drawings in which:

Figure 1 is a cut-away perspective view of the engine;-

Figure 2 is a section through the combustion equipment parts taken alonga vertical plane through the axis of the engine as indicated by thelines 11-11 in Figures 3 to and Figures 3 to 5 are sections on the linesIII-III, IV-IV and V-V in Figure 2.

As may be seen from Figure 1 the engine comprises a duct 1 having anopen forward end 2 and an open rear end 3. At the rear end the duct isconstricted by an inner wall 4 constituting a convergent-divergentnozzle through which the propulsive jet issues. Within a forward part ofthe duct is arranged an island member 5 having a conical forward end 6protruding through the end 2 of the duct. The annular gap between theconical end 6 and the end 2 of the duct constitutes an air intakeopening and the passage 7 between the island memberand the duct leadingrearwardly from the air intake opening constitutes a diflluser in whichthe velocity of the air is reduced and its pressure is increased inknown manner..

The arrangement of these parts has no essential connection with thepresent invention and further description of them is thereforeconsidered unnecessary. The invention resides in the arrangement of thecombustion equipment section of the engine, which is the part shown inFigure 2, and this part will now be described.

The island member 5 has a hollow rear end portion 8 enclosing a pilotcombustion zone 9 open at its downstream end. around a rear part of theisland member extend lengthwise of the member and outwardly across thepassage 7. Each vane 10 has an open forward end 11 and an open rearwardend 12 and comprises two internal partitions 13 and 14 dividing thehollow interior into a middle chamber 15, a front end chamber 16 and arear end chamber 17. The front end chambers 16 are connected by openings18 in the wall of the island member to a manifold chamber 19 surroundinga central rearwardly extending projection 20 provided with a fuelconduit 21 and carrying a fuel jet 22 arranged to disperse fuel in thedownstream direction into the pilot combustion zone 9. The front endchambers 16 thus act as passages conveying air from the passage 7 intothe pilot combustion zone 9 by way of the manifold chamber 19. To assistthe dispersion of fuel and products of combustion in the pilotcombustion zone 9 a ring of swirl producting blades 23 is providedradiating from the projection 20 adjacent the burner 22. As will beseen, the partitions 13 constituting the outer walls of the passagesconveying air into the pilot combustion zone slope generally inwardlyand rearwardly so as to deflect the air entering through the openforward end 11 progressively towards the openings 18.

The part 8 of the island member constituting the wall of the pilotcombustion zone 9 is slotted in way of the rear end chambers 17 of thevanes so that flame from the pilot combustion zone can disperseoutwardly through these chambers as indicated by the arrows 24 and issuefrom their downstream open ends 12. The chambers thus act as radiatingflame holding gutters. To assist outward dispersion of the flame thepartitions 14 constituting the bottom of the gutters slope generallyoutwardly and rearwardly so that the depth of the gutters at theirjunction with the wall 8 is greater than the depth of the gutters nearthe duct 1. These radiating gutters are supplemented by a ring-shapedflame holding gutter 25 of V-shaped section arranged intermediatelybetween the duct 1 and the pilot combustion zone wall 8. The ring-shapedgutter 25 opens into the radiating gutter chambers 17 at openings 26,that is to say the gutter 25 is made in three arcuate portions eachportion extending from an opening 26 in a side wall of one of the vanes10 to an opening 26 in the side wall of the next adjacent vane. As willbe seen from the drawing the average depth of the radiating gutters,that is to say their dimension lengthwise of the. duct, is. about fourto five times the Three hollow vanes 10 evenly spaced 7 depth of thering-shaped gutter, this feature assisting materially in obtaining agood outward spread of the flame from the pilot combustion zone.

The middle chamber 15 of each vane is used to house two pyrotechnicigniter cartridges 27. These cartridges are supported with their axesdisposed radially by tubular supports 28 attached. to the wall 8 of thepilot combustion zone around holes 29 in the wall through which flamefrom the cartridges may enter the pilot combustion zone. Holes 30 in theduct 1 permit easy insertion and removal of the cartridges, this beingan important advantage of the arrangement according to the inventionsince considerations of safety require that the cartridges shall not befitted until immediately before the engine is required for use. Afterthe cartridges have been inserted, the holes 30 are closed by covers 31which screw into threads formed in bosses 32 surrounding the holes.While a single cartridge might in favourable circumstances .servetostart combustion, duplication is necessary to guard against thepossibility of a fault in the cartridge, and experience has shown thedesirability of having as many as six cartridges in order to guarantee aperfect start under all operating conditions. The cartridges includeelectrical ignition devices connected to terminal members 33 projectinglaterally from the cartridges at their outer ends. As the cartridges areinserted, electrical connection is made between the terminal members 33and contact devices 34 carried by an outer wall 35 forming part of thestructure of the vane 10. All the contact devices 34 are electricallyconnected by suitable wiring (not shown) to a common contact device (notshown) carried by the duct 1. The wall 35 also carries nut plates 36receiving the threaded ends of bolts 37 which, with the aid of spacingsleeves 38, assist in the attachment of the internal parts to the duct1.

The part of the island member comprising the projection 20 and enclosingthe manifold chamber 19 is formed as a unitary light alloy casting withthe forward part of the vanes 10, including the partition 13, and

with three projections 39 spaced intermediately between the vanes 10. Aswill be seen from Figure 1 each projection 39 forms part of a fin 4i)tapering at each end and extending between the island member and theduct. That fin which is seen lowermost in the drawings is, in a mannermore particularly described and claimed in the specification ofco-pending application No. 692,002, made of stronger construction thanthe others and is connected to flanges 41 on the outside of the duct,whereby, in association with rear mounting elements 42, the engine isattached to a vehicle which is required to propel. The island member 5is thus supported from the vehicle, and the casing 1 is supported fromthe island member by the fins 40 and the vanes 10. The attachment of theduct to the fins 40 is by means of bolts 43, some of which screw intoholes tapped in the projections 39, as seen in Figure 2, and others ofwhich screw into holes 44 tapped into a forward part 45 (Figure l) ofeach fin which is made as a unitary light alloy casting with a part 46of the island member. A fuel supply pipe 41a can be attached to theunderside of the engine, to connect with passages (not shown) leadinginto the island member and thence to the fuel conduit 21.

Each projection 39 is connected to the central projection 29 by a part47 in which is formed a fuel conduit 48 branching from the fuel conduit21 and leading to a port 49 on each side of the projection 39. Fuelpassing through these ports enters conduits formed in each of a pair oflaterally projecting brackets 59 arranged one on each side of theprojection 39 and secured to it by bolts 51. The conduit in each bracketleads to two cor-axially arranged fuel jets 52 and 53 of which 52projects fuel in an upstream direction into the passage between theisland member and the duct between It will be understood therefore thatin addition to the pilot zone jet 22 there are six jets 52 projectingfuel upstream and six jets 53 projecting fuel downstream. The fuel soprojected is carried downstream by the'airflow and is ignited by theflame held by the radiating and ring-shaped flame holding gutters 17 and25 so that it burns in the part 54 of the duct downstream of thesegutters.

When the invention is applied as an afterburning device in a turbo-jetengine the island member may be the so-called exhaust bullet of theengine.

We claim:

1. A fuel burner comprising a duct, an island member in the duct havinga hollow rear end portion co'nstitut ing a pilot combustion zone open atits downstream end, a plurality of hollow vanes open at each endextending lengthwise along a rear part of the island member andoutwardly across the passage between the island member and the duct,each vane comprising two internal partitions dividing the hollowinterior into a middlecliamber and front and rear end chambers, openingsin the wall of the island member connecting the front and rear endchambers with the pilot combustion zone, means in each middle chamberfor supporting an igniter of a kind capable of projecting a flame,openings in the wall of the island member through which flame from theigniters may enter the pilot combustion zone, openings in the duct,normally closed by closure members, through which the igniters may beinserted and withdrawn, and means for dispersing fuel into the pilotcombustion zonev and into the passage between each adjacent pair ofhollow three-chamber vanes.

2. A burner according to claim 1 in which at the rear end of the islandmember there are at least one ringshaped flame-holding gutter arrangedintermediatelybetween the duct and the pilot combustion zone, theringshaped gutter opening into the rear chambers of the hollowthree-chamber vanes.

3. A burner according to claim 2 in which the dimension of the rearchambers in the lengthwise direction of the duct is two or more timesthat of the ring-shaped gutter in that direction.

4. A burner according to claim 1 in which the partitions between thesaid middle and rear end chambers slope outwards and rearwards.

5. A burner according to claim 1 in which the partitions between saidmiddle and front end chambers slope inwards and rearwards.

6. A burner according to claim 1 in which the island member is formedwith a manifold chamber surround-- ing a central rearwardly extendingprojection provided with a fuel conduit and carrying a-fuel jet arrangedto disperse fuel in the downstream direction into the pilot combustionzone. the manifold chamber being separated from the pilot combustionzone by a' ring of swirl-producing blades radiating from the projection,and being connected to the front end chambers of the hollow threechamber vanes by the openings in the wall of the island member.

'7. A burner according to claim 6 in which the part of the island membercarrying the rearwardly extending projection is provided with at leastas many radiating projections each provided with a fuel conduit as thereare hollow three-chamber vanes, these radiating projections extendinginto the passage between the island member and the duct between eachadjacent pair of hollow three-chamber vanes, and carrying fuel jets fordispersing fuel into the passage.

8. A burner according to claim 7 in which one such radiating projectionis provided extending into the passage between the island member and theduct between each adjacent pair of hollow-three-chamber vanes, eachprojection carrying a fuel jet arranged to project fuel in an upstreamdirection and a fuel jet arranged to project fuel in a downstreamdirection.

9. A burner according to claim 8 in which each radiating projectionforms part of a fin tapering at each end and extending between theisland member and the duct, the part of each fin constituted by theradiating projection carrying on each side a lateral projection providedwith a fuel conduit, each lateral projection carrying, in axialalignment with one another, a fuel jet arranged to project fuel in anupstream direction and a fuel jet arranged to project fuel in adownstream direction.

10. A burner according to claim 7 in which the parts of the vanesconstituting the front end chambers of the vanes are made as a unitarycasting with the part of the island member constituting the manifoldchamber and the central and radiating projections, and the part of theisland member constituting the wall of the pilot combustion zone and theparts of the vanes constituting the middle chambers and the rear endchambers are made of heat-resisting sheet material.

11. A burner according to claim 1 in which there are three three-chambervanes, and two igniters in the middle chamber of each vane.

References Cited in the file of this patent FOREIGN PATENTS

